1. Field of the Invention
The present invention relates to a rotor of a rotary electric machine, wherein a magnetic pole part and a inter-pole part are formed, and a plurality of rotor slot for inserting field coils into a inter-pole part are provided in the direction of internal circumference.
2. Description of the Related Art
A conventional rotor of an electric rotary machine, for example, a turbine generator is configured as shown in FIG. 14.
In a rotor of a turbine generator, a rotor core 1 is made of a single massive lump of steel to provide a mechanical strength, and a magnetic pole part 6 and a inter-pole part 6A are formed as shown in the drawing. In the inter-pole part 6A, a plurality of rotor slot 2 for inserting a winding is provided at regular intervals in the direction of the internal circumference of the rotor core 1, and teeth 11 are formed between the slots. A field coil 3 is housed in each rotor slot 2.
FIG. 15 is a sectional view of the outside diameter part of the rotor slot 2, showing the basic configuration of the field coil 3 inserted into the rotor slot.
As shown in the drawing, in the field coil 3, a plurality of field coil conductor 10 is stacked in the radial direction, and a slot insulator 8 is provided between the field coil conductor 10 and the inside surface of the rotor slot 2, an insulation block 7 is provided between the field coil conductor 10 and a rotor wedge 4 provided at the open end of the rotor slot 2, thereby ensuring insulation among the field coil conductor 10, the rotor core 1 becoming an earth potential, and the rotor wedge 4.
Between the rotor wedge 4 and insulation block 7, a slot dumper 9 may be provided to decrease an eddy current loss caused by a harmonic magnetic field generated in a not-shown stator.
Further, a subslot 5 serving as a ventilation path in the axial direction is provided at the bottom of the rotor slot 2, in being communicated to the bottom of the slot, a not-shown hole is provided as a ventilation path in the radial direction of the field coil 3 and rotor wedge 4, and the heat generated by Joule heating in the field coil 3 is cooled by a coolant supplied from the subslot 5.
As an example of a rotor of such a rotary electric machine, the shape, structure and arrangement of a slot are changed to decrease a voltage fluctuation rate, thereby improving stability (e.g., Jpn. Pat. Appln. KOKAI Publication No. 11-89132, and Japanese Patent No. 3303674).
To improve the efficiency of a rotary electric machine, it is necessary to decrease a field winding copper loss as one of the loss generated by a rotary electric machine. To increase the capacity of a rotary electric machine, it is necessary to increase a magnetic flux of a field magnetic by increasing a field magnetomotive force.
In contrast, when a field magnetomotive force is increased, a field coil is heated much more, and the efficiency of cooling the field coil needs to be increased as the field magnetomotive force is increased. In this case, also, the total cross section of a field coil conductor forming a field coil must be increased to decrease a field winding copper loss.
However, as the dimensions of a rotor slot are limited by the strength of a rotor, the cross section of a rotor slot cannot be increased, and a field magnetomotive force cannot be increased.